With the rapid development of mobile communication technologies, more and more users use wireless data services for communication. At present, terminals supporting wireless data services mainly include: a wireless data card and a mobile phone.
During the uplink transmission process of signals transmitted by a terminal, radio frequency signals are amplified by a PA (Power Amplifier, power amplifier, power amplifier for short) and amplified radio frequency signals are then transmitted by an antenna to the space. The PA is a major power-consuming element during the uplink transmission process of the terminal. If the efficiency of the PA is low, the power consumption of the entire equipment will be large. The power supply circuits of two types of terminals in the prior art are introduced respectively in the following.
As shown in FIG. 1, in a power supply circuit of a PA in a battery-powered terminal such as a mobile phone, VBAT is an output voltage, and the voltage is stable in the range of 3.7V˜4.2V, where the voltage is used as the power supply voltage of the PA.
As shown in FIG. 2, in a commonly used power supply circuit of a PA in a wireless data card, U1 is a direct current/direct current converter chip (that is, a DC/DC switch power chip). VIN is a working power supply of the wireless data card, where the power supply is provided by a portable computer through commonly-used peripheral interfaces, such as a USB (Universal Serial Bus, universal serial bus) interface, a PCMCIA (Personal Computer Memory Card International Association, Personal Computer Memory Card International Association) interface, or an ExpressCard interface.
      V    OUT    =            (              1        +                              R            1                                R            2                              )        ·          V      FB      is a power supply voltage of the PA, and VFB is a feedback reference value of the DC/DC switch power chip, where the value is a fixed value. Obviously, after R1 and R2 are fixed, the power supply voltage VOUT of the PA is also a fixed value.
In the prior art, the power supply voltage of the PA is constant. In practical application, the required output power of the PA changes along with a change of the network state of the terminal. It is known from properties of the PA that, under a prerequisite that the entire equipment satisfies a radio frequency index, if a required output power of the PA is reduced, the power supply voltage of the PA is reduced as well. In this case, the closer the actual power supply voltage of the PA is to the required output power of the PA, the higher the efficiency of the PA is. In addition, the PA has certain discreteness, and under the prerequisite that the entire equipment satisfies the radio frequency index, the required power supply voltage of the PA is different. However, in the prior art, the power supply voltage of the PA is a constant value and cannot change according to the change of the required power supply voltage, which thereby causes that the efficiency of the PA is low and the power consumption of the entire equipment is large.